Fiber-optic system for measuring temperature of rigid deformable media

Abstract

Background. Currently, during the construction of new nuclear power plants (NPP), its service life has been extended to 60 years, which requires the modernization of information and measurement systems that control many parameters of the dome of the NPP, including temperature parameters. The safety of the NPP as a whole depends on the accuracy of measuring the temperature of the cement base of the dome of the NPP. The measuring instruments used should not create additional electromagnetic interference during measurements, therefore, the use of fiber-optic measuring instruments is considered more preferable. The object of the study is a fiber-optic information and measurement system (FOIMS) of the stress-strain state of the protective shell of the NPP. The subject of the research is scientific and technical solutions of fiber-optic temperature sensors (FOTS) with a compensation channel, which are part of the nuclear power plant protective shell, installed in rigid deformable environments. The purpose of the study is to develop constructive, technological and structural solutions of the FOTS, providing the possibility of its application in rigid deformable environments with minimal dynamic error due to inertial processes in the sensor housing. Materials and methods. The main approach to achieve this goal is to adapt the previously developed technical solutions of the FOTS to the measurement conditions in rigid deformable media, which are the supporting parts of the dome of the NPP. Results. The structure is determined and the design of the FOTS with a compensation channel of the reflective type is developed. The relations between the coefficients of thermal expansion of the materials from which the structural elements of the FOTS are made, providing a reduction in the deformation of the protective housing and the sensitive element of the FOTS when the temperature changes, are determined. The initial distance between the mirror surface and the ends of the optical fibers located opposite the mirror surface, at which the sensor conversion function is linear, and the maximum sensitivity (up to 30%) and the modulation depth of the optical signal conversion (up to 50%) are determined. Conclusions. The design, technological and structural solutions of the FOTS with a reflective type compensation channel for the FOIMS of the protective shell of NPP placed in rigid deformable environments have been developed. The use of the developed fiber-optic temperature sensor will provide: reduction of internal stresses inside the deformable environment of the protective shell when its temperature changes; reduction of the dynamic error of temperature measurement; increase in the accuracy of measuring the temperature of the protective shell.

Keywords

• information-measuring system
• temperature
• fiber-optic sensor
• nuclear power plants
• protective shell
• rigid deformable medium
• micro-optical system
• block diagram